My experience with dystonia is very similar to yours. Treatment is a trial and error process that takes patience and time.
What works
for one person may not work for another. Your best bet is to work w/a neurologist who specializes in movement disorders. If you don't get good results, find another doctor. My doctor told me that even experts don't fully understand dystonia. If you're worried about side effects from Gabapentin, ask for a smaller dose and work up.